In prior art, radiation detection apparatuses, in particular, X-ray detection apparatuses which detect X-rays have been used in various fields such as industrial nondestructive testing, medical diagnosis, and scientific research including structural analysis.
Among X-ray detection apparatuses, a high-sensitivity and a high-definition X-ray detection apparatus provided with an X-ray detection panel having a photodetector and a fluorescent layer has been known. The photodetector includes a photoelectric conversion element section in which a plurality of photosensors and a plurality of thin-film transistors (TFTs) are arranged in a two-dimensional manner. The fluorescent layer is directly formed on the photodetector. The fluorescent layer converts an X-ray into light which can be detected by the photoelectric conversion element section.
The X-ray detection panel is supported by one surface of a plate-shaped support member. A circuit board is supported by the other surface of the support member, and drives the X-ray detection panel. The X-ray detection panel and the circuit board are electrically connected to each other through a flexible circuit board. A detection integrated circuit is provided on the flexible circuit board, or at one end of the flexible circuit board.
When the X-ray detector is operated, the circuit board and the detection integrated circuit generate heat. A part of the generated heat is radiated into air inside a housing of the X-ray detection apparatus. However, most of the heat moves to members having a lower temperature based on heatconduction.
Therefore, the heat generated in the circuit board and the detection integrated circuit is conducted to the support member which supports the circuit board. In addition, the heat conducted to the support member is conducted to the X-ray detection panel having a lower temperature.
When the heat is conducted to the X-ray detection panel, a temperature of the X-ray detection panel increases, and an operation temperature becomes a high temperature. Then, a dark current of the photoelectric conversion element and a leakage current of the TFTs increase and an amount of fixed noise fluctuates, which results in a problem causing unevenness in an image.
The heat generation quantity of the whole detection integrated circuit is not uniform, nor is the heat generation quantity of part of the detection integrated circuit. The thermal conductivity of the whole detection integrated circuit is not uniform, nor is the thermal conductivity of part of the detection integrated circuit. Therefore, partial fluctuation occurs in the temperature of the X-ray detection panel. Thus, values of the dark current and the leakage current fluctuate, and the fixed noise changes in part of the X-ray detection panel.
To solve the above problem, a method of cooling the detection integrated circuit and the X-ray detection panel by using a cooling device has been proposed. As the cooling device, although there is a cooling device adopting a natural radiational cooling system, a peltier element or a cold-water circulation device is used in order to obtain sufficient cooling performance.
Further, a method of energizing the X-ray detection apparatus for 24 hours before use to make uniform a variation of the leakage current has been also proposed.
On the other hand, a method of releasing heat generated in the detection integrated circuit to the housing through a thermally conductive member has been proposed.